% ---------------------------------------------------------------------
% Capacitor: i(t) adianta v(t) em 90°.
% Requer pgfplots (habilitado via engine.opts na aula).
% ---------------------------------------------------------------------
\begin{tikzpicture}
\begin{axis}[
  width=18cm, height=8.5cm,
  axis lines=middle,
  label style={font=\Large},
  tick label style={font=\Large},
  xlabel={$\omega t$ (rad)}, ylabel={Amplitude},
  xtick={0,90,180,270,360},
  xticklabels={$0$,$\pi/2$,$\pi$,$3\pi/2$,$2\pi$},
  ytick=\empty,
  ymin=-1.4, ymax=1.4,
  xmin=0, xmax=360,
  domain=0:360, samples=200,
  enlargelimits=false,
  legend pos=north east,
  legend style={font=\Large},
  line width=2.2pt,
]
\addplot[blue!70!black, line width=2.6pt] {cos(x)};
\addlegendentry{$v(t)$}
\addplot[red!70!black, line width=2.6pt, dashed] {cos(x+90)};
\addlegendentry{$i(t)$}
\end{axis}
\end{tikzpicture}